update limitation of converter tool (#1401)
update limitation of converter tool (#1401)

* update limitation of converter tool

* typo

* clarify a bit per Mandar's req

* good catch from Guang

istio/istio.io,linsun/istio.github.io,linsun/istio.github.io,ZackButcher/istio.github.io,linsun/istio.github.io,istio/istio.io,geeknoid/istio.github.io,linsun/istio.github.io,ZackButcher/istio.github.io,ZackButcher/istio.github.io,istio/istio.io,geeknoid/istio.github.io,ZackButcher/istio.github.io,istio/istio.io,istio/istio.io,istio/istio.io,geeknoid/istio.github.io,geeknoid/istio.github.io,linsun/istio.github.io,geeknoid/istio.github.io,istio/istio.io